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In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be?

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In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be 0.5.

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Description :

In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was?

Answer :

In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was unity.

Description :

State any two disadvantages of one wattmeter method of measurement of 3 phase power.

Answer :

State any two disadvantages of one wattmeter method of measurement of 3 phase power. Disadvantages of one wattmeter method:- 1. Only used for balanced load 2. It can not be used for ... connection then neutral point must be available 4. Delta connection must be opened to connect current coil.

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Answer :

In a low power factor wattmeter the compensating coil is connected in series with pressure coil.

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Answer :

In a low power factor wattmeter the pressure coil is connected to the load side of the current coil.

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Answer :

In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at 120°.

Description :

Answer :

In a single phase power factor meter the phase difference between the currents in the two pressure coils is exactly 90°.

Description :

While measuring power in a three phase load by two wattmeter method, the reading of two wattmeter are equal and opposite, when (a) load is balanced (b) power factor is unity (c) phase angle is between 60° to 90° (d) the load is purely inductive 

Answer :

 Option (d)  Load is purely inductive 

Description :

Answer :

The two pressure coils of a single phase power factor meter have the same dimensions and the same number of turns.

Description :

 In the measurement of power of balanced load by two wattmeter method in a 3-phase circuit, The readings of the wattmeters are 4 kW and 2 kW respectively, the later is being taken after reversing the connections of current coil. the power factor and reactive power of the load is A) 0.2 & 6 kVAR B) 0.2 & 6 √3 kVAR C) 0.32 & 2 kVAR D) 0.32 & 2 √3 kVAR

Answer :

 In the measurement of power of balanced load by two wattmeter method in a 3-phase circuit, The readings of the wattmeters are 4 kW and 2 kW respectively, the later is being taken after reversing the ... of current coil. the power factor and reactive power of the load is 0.2 & 6 √3 kVAR

Description :

Measurement of power and power factor of a 3-phase system by two wattmeter method can be obtained in case of  1. Balanced load and balanced source  2. Balanced source with 3-phase 3-wire unbalanced load  3. Unbalanced source with 3-phase 3-wire balanced load  4. Balanced source with 3-phase 4-wire unbalanced load  5. unbalanced and unbalanced source    (a) 1 only (b) 2, 3 and 5 (c) 1, 2, 3, 4 and 5 (d) 1, 2, 3 and 5 

Answer :

Measurement of power and power factor of a 3-phase system by two wattmeter method can be obtained in case of  1. Balanced load and balanced source  2. Balanced source with 3-phase 3-wire unbalanced load  3. Unbalanced source with 3- ... b) 2, 3 and 5 (c) 1, 2, 3, 4 and 5 (d) 1, 2, 3 and 5 

Description :

In two -wattmeter method of power measurement, if one wattmeter shows negative reading, then the power factor of the circuit is treated as (A) Unity (B) Lagging (C) Leading (D) Zero

Answer :

Lagging   power   factor.

Description :

For power measurement of three phase circuit by two wattmeter method, when the value of power factor is less than 0.5 lagging:

Answer :

For power measurement of three phase circuit by two wattmeter method, when the value of power factor is less than 0.5 lagging: One of the wattmeter connections will have to be reversed

Description :

Answer :

The power factor of a single phase load can be calculated if the instruments available are three ammeters or three voltmeters.

Description :

Explain the effect of power factor on wattmeter reading in two wattmeter method for power measurement.

Answer :

Effect of P.F. on Reading of Wattmeter in Two Wattmeter Method:

Description :

Merits of two wattmeter method

Answer :

Advantages of Two Wattmeter Method for 3-Phase Power Measurement: 1) It is used for balanced as well as unbalanced load. 2) For the star type load, it is not necessary to ... reactive volt-amperes for balanced loads also. 7) The circuit connections are independent of load connection.

Description :

List one advantage and one disadvantage of one wattmeter method. 

Answer :

Advantages:  1) Only one wattmeter is used.  2) Less number of connections.  3) Cost required is less.  Disadvantages:  1) Used only for 3- Φ balanced load and not for ... be accessible for connecting the Pressure coil.  3) Delta connection must be opened to connect current coil. 

Description :

Answer :

In the case of power measurement by two wattmeter method in a balanced 3Φ system with a pure inductive load both the Wattmeter will indicate the same but of opposite sign.

Description :

In the measurement of power by two wattmeter method, when the readings of the two wattmeters are equal, the power factor is (A) Zero (B) Leading (C) Lagging (D) Unity

Answer :

In the measurement of power by two wattmeter method, when the readings of the two wattmeters are equal, the power factor is Unity

Description :

In the measurement of three phase power by two wattmeter method, if the two wattmeter readings are equal then power factor of the circuit is  (A) 0.8 lag (B) Unity (C) 0.8 lead (D) Zero 

Description :

The power consumed by a balanced 3-ph load is measured by two-wattmeter method. The meter readings are 8 kW and 4 kW. The power factor of the load is (A) zero (B) 0.5 (C) between zero and 0.5 (D) between 0.5 and unity

Answer :

The power consumed by a balanced 3-ph load is measured by two-wattmeter method. The meter readings are 8 kW and 4 kW. The power factor of the load is between 0.5 and unity

Description :

Draw and explain bulk correction method for power factor & control.

Answer :

Bulk correction method for power factor & control: i) Here individual starter controls the capacitors located at distribution panel. ii) Centralized compensation is employed in large industrial plants where many ... capacitor units in steps to maintain P.F. more than preset limit (0.95). 

Description :

Answer :

A power factor meter has one current circuit and two pressure circuits.

Description :

In an alternator at lagging power factor the generated voltage per phase as compared to that at unity power factor?

Answer :

In an alternator, at lagging power factor the generated voltage per phase as compared to that at unity power factor must be more than terminal voltage.

Description :

With a neat sketch explain working of 1 phase dynamometer type power factor meter.

Answer :

Working of 1 phase dynamometer type power factor meter : The current coil is connected in series with load. Two pressure coils marked as A and B are connected across the supply terminals ... becomes stationary and the pointer shows steady deflection corresponding to the power factor of the load. 

Description :

What is the power factor when a single phase watt meter operating on 200 V and 5 A for 5 hours makes 2016 revolutions and the meter constant in revolution is 420? A) 0.04 B) 1.04 C) 0.96 D) None of these

Answer :

What is the power factor when a single phase watt meter operating on 200 V and 5 A for 5 hours makes 2016 revolutions and the meter constant in revolution is 420? A) 0.04 B) 1.04 C) 0.96 D) None of these

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Answer :

The power factor of a single-phase induction motor is usually lagging.

Description :

Answer :

The resistance in the circuit of the moving coil of a dynamometer wattmeter should be high.

Description :

The torque produced in wattmeter is proportional to

Answer :

A

Description :

Answer :

The pressure coil of a wattmeter should be connected on the supply side of the current coil when load impedance is high.

Description :

Answer :

A dynamometer wattmeter can be used for both D.C. and A.C.

Description :

Answer :

An induction wattmeter can be used for A.C. 

Description :

The potential coil of a single phase dynamometer wattmeter has 4840 Ohm resistance. Voltage across the load is 220 V. With the potential coil connected on the load side, the meter indicates 100 W. Approximate percentage error due to wattmeter connection is (A) 11% (B) 9% (C) 1.1% (D) 3%

Answer :

The potential coil of a single phase dynamometer wattmeter has 4840 Ohm resistance. Voltage across the load is 220 V. With the potential coil connected on the load side, the meter indicates 100 W. Approximate percentage error due to wattmeter connection is 11%

Description :

Use Voltmeter, ammeter, wattmeter to determine active, reactive and apparent power consumed in given R-L series circuit, draw phasor diagram.

Answer :

Practical Significance In the industry environment Electrical Engineering diploma graduate are expected to measure basic parameters like voltage, frequency, time period etc. for R-L series circuits. Therefore ... /varying L. 7. Draw the phasor diagram for each of reading for verification.

Description :

Power factor of an inductive circuit is usually improved by connecting capacitor to it in?

Answer :

Power factor of an inductive circuit is usually improved by connecting capacitor to it in parallel.

Description :

Draw the circuit diagram for:- i) Measurement of active power in 3-phase load circuit using two wattmeter. ii) Measurement of reactive power in 3-phase load circuit using one wattmeter.

Answer :

(i) Measurement of active power in 3- phase load circuit using two- wattmeter: (ii) Measurement of reactive power in 3- phase load circuit using one wattmeter

Description :

The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA The power drawn by the circuit is?

Answer :

The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA The power drawn by the circuit is 32 kW.

Description :

Answer :

Yes, we can make the power factor of synchronous motor leading by adjusting its excitation.

Description :

The power in a 3-phase load is measured by two watt meters. If one watt meter reads zero, then the load power factor is (A) Zero (B) 0.5 (C ) 0.866 (D) unity 

Description :

List any two methods of reactive power measurement in 3 phase circuit.

Answer :

Methods of reactive power measurement in 3 phase circuit: (i) Two single phase wattmeter method (ii) One single phase wattmeter method

Description :

In a synchronous generator delivering lagging power factor load  (1) the excitation emf leads terminal voltage by the power angle (2) the excitation emf lags terminal voltage by the power angle (3) excitation emf leads the terminal voltage by the power factor angle (4) excitation emf lags the terminal voltage by the power factor angle

Answer :

In a synchronous generator delivering lagging power factor load the excitation emf leads terminal voltage by the power angle

Description :

The benefit of power factor correction in a power system is (A) lower power consumption (B) increased demand charge (C) reduced load carrying capabilities in existing lines (D) reduced voltage profile

Answer :

The benefit of power factor correction in a power system is lower power consumption

Description :

Answer :

In a distribution system, in order to improve power factor, the synchronous capacitors are installed at the receiving end.

Description :

Answer :

For high value of diversity factor, a power station of given installed capacity will be in a position to supply more number of consumers.

Description :

The power factor at resonance in R-L- C parallel circuit is?

Answer :

since a rlc circuit at resonance behaves like a pure resistive circuit, i.e there is no phase difference between current and voltage, hence the power factor is unity.

Description :

Capacitors for power factor correction are rated in?

Answer :

Capacitors for power factor correction are rated in kVAR.

Description :

A transformer has negative voltage regulation when its load power factor is   (1) Zero (2) Unity (3) Leading (4) Lagging

Answer :

Leading

Description :

The power factor angle and torque angle of a salient pole synchronous generator drawing a current of 1.0 pu from a lagging load are 45o and 15o, respectively. The direct axis and quadrature axis currents, respectively, are (A) 0.5 pu, 0.866 pu (B) 0.866 pu, 0.5 pu (C) 0.707 pu, 0.707 pu (D) 0.5 pu, 0.5 pu

Answer :

The power factor angle and torque angle of a salient pole synchronous generator drawing a current of 1.0 pu from a lagging load are 45o and 15o, respectively. The direct axis and quadrature axis currents, respectively, are 0.866 pu, 0.5 pu

Description :

The power factor of a D.C. circuit is always?

Answer :

The power factor of a D.C. circuit is always unity.

Description :

Answer :

When a D.C. series motor is connected to A.C. supply, the power factor will be low because of high inductance of field and armature circuits.

Description :

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?

Answer :

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because stator supply is not required to produce magnetic field.

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